Cluster of hard-tubed coral (?) polyps on Australian live rock.

[Tired]

These little guys came in on some Australian rock. I thought this was a colony of dead tubeworms or vermetid snails, but it's now revealed itself to be something like a coral. Maybe a tube anemone? Do those build hard tubes? They're pretty tiny- the tubes are about half an inch long apiece. Cute little things, with those tiny green spots in the centers. 

[jservedio]

Looks like colonial hydroids to me. I've got a bunch of them in various colors and a lot of them fluoresce under blue/UV. They are definitely considered a pest and can spread like wildfire if you aren't super careful about particulates. Broadcast feeding corals is a no-no with them if you want to keep them and keep them under control.

 

If you want to get rid of them, they are pretty easy to kill off by making a flat pancake of epoxy putty that's maybe 1/2" bigger than the colony in all directions and placing it over all their tubes - you don't have to mash it down, just prevent them from getting light and particulates and they'll be gone eventually and then you can remove the epoxy. Theoretically you can pluck their tubes out, but they are extremely hard to rip out.

[Tired]

Ah, yeah, that is an option, isn't it. I'd forgotten about those.

 

Do they spawn, or do they spread from their original point? I'd like to give these a chance, see if they're a species that behaves itself reasonably well, as I know some hydroids aren't particularly invasive. If they spread outward, that's easy enough to keep an eye on, but them potentially starting to pop up everywhere a la blue clove polyps would be an issue. 

 

I already have a couple species of hydroid in here from some Florida rock. Though, I also have a hydroid-eating nudibranch, so that situation might resolve itself.

[jservedio]

36 minutes ago, Tired said:

Ah, yeah, that is an option, isn't it. I'd forgotten about those.

 

Do they spawn, or do they spread from their original point? I'd like to give these a chance, see if they're a species that behaves itself reasonably well, as I know some hydroids aren't particularly invasive. If they spread outward, that's easy enough to keep an eye on, but them potentially starting to pop up everywhere a la blue clove polyps would be an issue. 

 

I already have a couple species of hydroid in here from some Florida rock. Though, I also have a hydroid-eating nudibranch, so that situation might resolve itself.

I'd think it depends on the species - I know mine are able to spread far and wide! They are really pretty, especially the ones that fluoresce green under UV, and they don't sting very badly. The only coral I've ever had them outcompete are small zoas and I've had them for probably 6 or 7 years now. Other corals I've had come up against them are a nasty favia, acros, and montis - all of which just grow right over them. They don't spread super fast, so even if they became a problem they aren't really hard to kill back, just takes a while to starve them out.

 

To give you an idea of how weakly they sting, here's the base of my Red Planet currently growing over a field of them. Sorry for the grainy picture, but you can see them touching and not really harming the acro. Cap is also growing over them too:

 

[Tired]

Ah, yeah, that's not very nasty. I'll keep an eye on mine; I'd rather not have the rocks covered in stinging copepod-eaters for my tank full of small fish, but it's worth giving them a chance. I'll get 'em with Aiptasia-X or putty if they start spreading too fast. 

[jambon]

I have a few small colonies of the same or very similar hydroids... they are not invasive in my tank. 2 clumps about an inch in diameter, just a little more eye candy.😊

[mcarroll]

About how big around is each polyp?  It's hard to gauge in the pic.  Seems like it could also be a little colony of Snake Polyps.

 

FYI, hydroids (aka hydroid jellyfish) are sometimes reef friendly in the wild.  I think there's an assumption about them always being a pest....probably from one anecdote XX years ago from someone who was just phobic of things like this.  🤷‍♂️  If you look at hydroid threads, it seems like the phobic situation.....no actual reports of them causing actual problems....just "I'm scared; how can I get rid of it???"

 

Broadcast feeding is probably what makes them get happy.....so if they seem too happy, stop broadcast feeding.    It's a wasteful coral-feeding strategy anyway.....not really recommended in most cases.

[Tired]

The tubes are maybe 2-3mm across, so they're pretty tiny. Snake polyps are bigger, right? 

 

I'm not planning on trying to broadcast feed my corals, since that doesn't work so well for LPS, but I do want to have some amount of particles available for things like the little feather dusters, tunicates, and my porcelain crabs. I like to encourage all the harmless variety of life.